in script when I type rigidbody it says it was unexpected. Why?

Questions & Answers
1

It’s possible that this is due to Unity 5’s changes in the GetComponent function. Where as formerly you could use short words to access Unit-specific components like RigidBodies (rigidbody), now it HAS to be GetComponent().

2

Probably because

GetComponent<Rigidbody>()

was expected.